1. Field of the Invention
The present invention relates to denture cleanser compositions and, more particularly, denture cleanser tablet compositions which have long lasting flavor and taste.
2. Description of the Art
Conventional denture cleanser tablets are typically formulated with effervescent systems, bleaching agents, surfactants, builders, chelating agents and/or enzymes to remove unsightly stains and debris from dentures. The addition of flavor oils to denture cleanser tablet formulations has greatly increased the appeal of these products to consumers because they impart a fresh, for example minty, odor and taste to the dentures. However, it is known that tablet aroma changes during storage and studies have shown that denture cleanser tablet users are very sensitive to and are able to detect even slight changes in tablet aroma. Hence denture cleanser tablet aroma is a very important commercial attribute of these products. The known denture cleanser tablets, however, tend to have their aroma change during storage.
Layered denture cleansing tablets are known. U.S. Pat. No. 3,962,107 to Levin et al., for example, discloses a two layer denture cleanser tablet including an enzyme layer and an active oxygen layer. This formulation is designed to overcome the problem of the inactivating effect of the active oxygen compounds on the enzyme during the shelf life period as well as in the water solution when the tablet is placed in water with the dentures to be cleaned. In Levin's preferred composition, the enzyme layer contains sodium bicarbonate, polyvinyl pyrrolidone, magnesium lauryl sulfate, citric acid, polyethylene glycol 6000 and the enzyme. The active oxygen layer contains potassium monopersulfate, sodium perborate, citric acid, sodium bicarbonate, sodium lauryl sulfoacetate, polyvinyl pyrrolidone, magnesium lauryl sulfate and polyethylene glycol 6000. In one example, the flavorant in Levin's composition was incorporated in the enzyme layer. U.S. Pat. Nos. 4,256,599 to Krisp et al. and 4,417,993 to Gergely, and European Pat. Appl. Nos. 0151203 and 0248936 also disclose denture cleanser tablets having two layers.
The prior art, however, has not attempted to preserve the flavor and aroma of denture cleanser tablets using a layered arrangement. Indeed, the prior art has apparently not recognized the problem of flavor and/or aroma degradation, let alone the cause or solution of it.
It is an object of the present invention to provide layered denture cleanser tablet compositions having a fresh aroma and fresh taste even after prolonged storage. This and other objects will become apparent from the following description.